For many years, portable computers have been getting smaller and smaller. The principal size-limiting component in the effort to produce a smaller portable computer has been the keyboard. If standard typewriter-size keys are used, the portable computer must be at least as large as the keyboard. Miniature keyboards have been used on portable computers, but the miniature keyboard keys have been found to be too small to be easily or quickly manipulated with sufficient accuracy by a user.
Incorporating a full-size keyboard in a portable computer also hinders true portable use of the computer. Most portable computers cannot be operated without placing the computer on a flat work surface to allow the user to type with both hands. A user cannot easily use a portable computer while standing or moving. In the latest generation of small portable computers, called Personal Digital Assistants (PDAs), companies have attempted to address this problem by incorporating handwriting recognition software in the PDA. A user may directly enter text by writing on a touch-sensitive panel or display screen. This handwritten text is then converted into digital data by the recognition software. Unfortunately, in addition to the fact that printing or writing with a pen is in general slower than typing, the accuracy and speed of the handwriting recognition software has to date been less than satisfactory. To make matters worse, today's handheld computing devices which require text input are becoming smaller still. Recent advances in two-way paging, cellular telephones, and other portable wireless technologies has led to a demand for small and portable two-way messaging systems, and especially for systems which can both send and receive electronic mail (e-mail).
It would therefore be advantageous to develop a much smaller keyboard for entry of text into a computer. As the size of the keyboard is reduced, the user encounters greater difficulty selecting the character of interest. In general there are two different types of keyboards used in such portable devices. One is the familiar mechanical keyboard consisting of a set of mechanical keys that are activated by depressing them with a finger or thumb. However, these mechanical keyboards tend to be significantly smaller than the standard sized keyboards associated with typewriters, desktop computers, and even laptop computers. As a result of the smaller physical size of the keyboard, each key is smaller and in closer proximity to neighboring keys. This increases the likelihood that the user depresses an unintended key, and the likelihood of keystroke errors tends to increase the faster the user attempts to type.
Another commonly used type of keyboard consists of a touch-sensitive panel on which some type of keyboard overlay has been printed, or a touch-sensitive display screen on which a keyboard overlay can be displayed. Depending on the size and nature of the specific keyboard, either a finger or a stylus can be used to interaction the panel or display screen within the area associated with the key that the user intends to activate. Due to the reduced size of many portable devices, a stylus is often used to attain sufficient accuracy in interactioning the keyboard to activate each intended key. Here again, the small overall size of such keyboards results in a small area being associated with each key so that it becomes quite difficult for the average user to type quickly with sufficient accuracy.
One area of prior development in mechanical keyboards has considered the use of keys that are much smaller than those found on common keyboards. With smaller keys, the user must take great care in controlling each key press. One approach (U.S. Pat. No. 5,612,690) proposes a system that uses up to four miniature keys in unison to define primary characters, e.g. the alphabet, and nests secondary character rows, e.g. numbers, between primary character rows. Selecting a secondary character involves depressing the miniature key from each of the surrounding primary characters. Grouping the smaller keys in this fashion creates a larger apparent virtual key composed of four adjacent smaller keys, such that the virtual key is large enough to be depressed using a finger. However, the finger must interaction the keys more or less precisely on the cross-hairs of the boundaries between the four adjacent keys to depress them in unison. This makes it still difficult to type quickly with sufficient accuracy.
Another area of prior development in both touch screen and mechanical keyboards has considered the use of a much smaller quantity of full-size keys. With fewer keys, each single key press must be associated with a plurality of letters, such that each key activation is ambiguous as to which letter is intended. As suggested by the keypad layout of a touch-tone telephone, many of the reduced keyboards have used a 3-by-4 array of keys, where each key is associated with three or four characters (U.S. Pat. No. 5,818,437). Several approaches have been suggested for resolving the ambiguity of a keystroke sequence on such a keyboard. While this approach has merit for such keyboards with a limited number of keys, it is not applicable to reduced size keyboards with a full complement of keys.
Another approach in touch screen keyboards has considered analyzing the immediately preceding few characters to determine which character should be generated for a keystroke that is not close to the center of the display location of a particular character (U.S. Pat. No. 5,748,512). When the keyboard is displayed on a small touch screen, keystrokes that are off-center from a character are detected. Software compares the possible text strings of probable sequences of two or three typed characters against known combinations, such as a history of previously typed text or a lexicon of text strings rated for their frequency within a context. When the character generated by the system is not the character intended by the user, the user must correct the character before going on to select the a following character because the generated character is used to determine probabilities for the following keystroke.
Recently, various input devices have been introduced that provide new opportunities for user interaction with computers, PDAs, video games, cell phones, and the like.
For example, the laser-projection keyboard offered by companies such as Virtual Keyboard (see http://www.vkb.co.il/) and Canesta (see http://www.canesta.com/) is a projection keyboard that is capable of being fully integrated into smart phones, cell phones, PDAs, or other mobile or wireless devices. The laser-projection keyboard uses a tiny laser pattern projector to project the image of a full-sized keyboard onto a convenient flat surface, such as a tabletop or the side of a briefcase, between the device and the user. The user can then type on this image and the associated electronic perception technology instantly resolves the user's finger movements into ordinary serial keystroke data that are easily used by the wireless or mobile device.
Also known are muscle-sensing keyboards, such as the Senseboard® virtual keyboard (see, for example, http://www.senseboard.com/), which typically consist of a pair of hand modules with a pad that is placed in the palm of the user's hand. A muscle-sensing keyboard enables a user to type without the physical limitations of a standard keyboard. This type of virtual keyboard typically uses sensor technology and artificial intelligence, such as pattern recognition, to recognize the characters that a user is typing. The keyboard detects the movements of the fingers and relates them to how a touch typist would use, for example, a standard QWERTY keyboard. The information thus generated is then transferred to, for example, a mobile device, such as a personal digital assistant (PDA) or a smart phone using, for example, a cable or a Bluetooth wireless connection.
Yet another virtual keyboard is the fabric keyboard (see, for example, http://www.electrotextiles.com/). Such keyboards provide three axes (X, Y and Z) of detection within a textile fabric structure approximately 1 mm thick. The technology is a combination of a fabric sensor and electronic and software systems. The resulting fabric interface delivers data according to the requirements of the application to which it is put. The three modes of sensor operation include position sensing (X-Y positioning), pressure measurement (Z sensing), and switch arrays. Thus, a keyboard can be constructed that detects the position of a point of pressure, such as a finger press, using the interface's X-Y positioning capabilities. The system works even if the fabric is folded, draped, or stretched. A single fabric switch can be used to provide switch matrix functionality. Interpreting software is used to identify the location of switch areas in any configuration, for example to implement keyboard functionality.
Unfortunately, a major obstacle in integrating such virtual keyboards into various data receptive devices is fact that it is very difficult to type accurately when there are no physical keys on which to touch-type. In this regard, the user must rely entirely on hand-eye coordination while typing. Yet most touch typists are taught to type without looking at the keys, relying on tactile feedback instead of such hand-eye coordination. In such virtual keyboards there is literally no point of registration for the user's hands, and thus no tactile feedback to guide the user as he types.
For all of the preceding systems, the fundamental problem is that the specific activations that result from a user's attempts to activate the keys of a keyboard do not always precisely conform to the intentions of the user. On a touch screen keyboard, the user's finger or stylus may hit the wrong character or hit between keys in a boundary area not associated with a specific character. With a miniaturized mechanical keyboard, a given key press may activate the wrong key, or may activate two or more keys either simultaneously or with a roll-over motion that activates adjacent keys in a rapid sequence. And with a virtual keyboard, the lack of tactile feedback allows the user's fingers to drift away from the desired key registrations. Other examples include common keyboards operated by users with limited ranges of motion or motor control, where there is a limited ability to consistently strike any particular space or key; or where the limb, such as in the case of an amputee, or the gloved hand or finger, or the device used to make the entry, such as a stylus, is far larger than the targeted key or character space.
It would be advantageous to provide an enhanced text entry system that uses word-level disambiguation to correct inaccuracies in user keystroke entries automatically, especially with regard to virtual keyboards.